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Benefits of Urban Trees

Urban trees have been considered as a tool to help reduce stormwater runoff generation by intercepting, infiltrating, and evaporating significant amounts of rainwater. If improperly designed, new urban developments will lead to an increase of impervious surface areas, which will be responsible for an increasing amount of stormwater runoff. Strategic tree planting and maintenance of existing street trees can decrease stormwater runoff.

A recent survey in the State of California found that average annual per tree management expenditure is $19, and the benefit is $110.63, thus a value of $5.82 in benefit is returned for every $1 spent​. A similar return on urban tree investment was reported as $5.60 in New York. Trees are becoming key components of urban green infrastructures. Below are a brief summary of many benefits of urban trees, as well as the monetary values associated with it (summarized from McPherson et al. (2016).) To learn more information please see the detail assessment.

Environmental and Economic Benefits

Stormwater ManagementIt was estimated that the annual benefit of avoided stormwater treatment and flood control costs associated with rainfall interception of urban trees in California was $41.5million US dollars. And the annual value per street tree of services was reported from $3.78 to as high as $29.91 in some cities in the United States (McPherson et al., 2016).

Carbon Reduction The amount of CO2 sequestered each year by street trees is about 375,704 t per year and the net annual CO2 removed from the atmosphere per tree ranges from 50.6kg/year to 93.3kg/year. Planting trees remains one of the cheapest, most cost effective means of drawing excess CO2 from the atmosphere. The updated values of avoided CO2 emissions by street trees was about $16.53per t CO2 (McPherson et al., 2016).

Cooling Effect Evapotranspiration, alone or in combination with shading effect, could help reduce peak summer temperature by 1-5°C. Annual electricity saving from air conditioning reduction by urban tree was 74.9 kWh/year per tree on average, and the total monetary value of energy saving per street tree was about $11.08 on average (McPherson et al., 2016).​Air QualityStreet trees are estimated to remove 0.29kg/year of air pollutants (e.g. volatile organic hydrocarbons [VOCs], NO2, SO2, PM10) from the atmosphere and the net annual value of trees’ effects on air quality is $18.15 million (McPherson et al., 2016).

Property ValuesAesthetic values provided by urban trees are not negligible. Green spaces created by urban trees foster the sense of community, and form local identity and landmark. Annual property values benefited by per street tree range $16.19 to $150.09 in the State of California (McPherson et al., 2016).

Social Benefits

Human Health and Well-beingTrees and green spaces in urban environments also provide benefits to human health and well-being. For example, trees’ role in filtering air is critical to support the physical health of humans. Research also suggested that accessing to nature has positive psychological impacts and can be part of an effective strategy to prevent mental ill health (Maller et al., 2006; Nesbitt et al., 2015).

Community Cohesion and Social Well-beingImproved community cohesion was identified as a key social benefits of urban trees by creating a sense of place, a local identity and a system of landmarks (GreenBlue Urban, 2016). Maas et al. (2009) found that “greenness" within one km had a positive effect on social well-being. Green spaces provide recreational opportunities and aesthetic benefits, as well as help residents develop a sense of community and attachment to neighbourhoods, increase social contacts and decrease the feelings of social isolation, which can all contribute to a greater sense of social well-being (Nesbitt et al., 2015).